1. Field of the Invention
The present invention relates to a composition of a conducting polymer and an organic opto-electronic and an organic electronic device employing the same. More particularly, the present invention relates to a composition including a conducting polymer doped with an ionomer, which has a low water uptake, has a low content of by-products (or impurities) produced by a decomposition reaction with electrons, and can physically crosslink with the conducting polymer, and an opto-electronic device having increased device performance such as device efficiency and lifetime by using the composition.
2. Description of the Related Art
Opto-electronic devices convert light energy into electric energy or electric energy into light energy, and examples thereof include organic electroluminescent devices, solar cells, and the like. Electronic devices use electrical current and voltage to modulate current with function of voltage or vice versa, and examples thereof include an organic transistor, an organic memory device and the like. At present, many studies regarding the formation of a conducting polymer film are being conducted to improve the device performance (or device current efficiency) of an opto-electronic device by efficiently transporting electronic charges injected from the electrodes of the device, i.e., holes and electrons into the device.
In particular, an organic electroluminescent device is an active device in which an electron and a hole recombine in a fluorescent or phosphorescent organic compound thin film (hereinafter referred to as an organic film) when an electric current is supplied to the organic film, thereby emitting light. Generally, the organic electroluminescent device has a multi-layer structure including a hole injection layer using a conducting polymer, an emissive layer, an electron injection layer, etc., to improve the efficiency of the device and reduce a driving voltage, rather than having only the emissive layer as an organic layer.
An aqueous PEDOT (Poly(3,4-ethylene dioxythiopene))-PSS (poly(4-styrenesulfonate)) solution, which is commercially available as Baytron-P from Bayer AG, is widely used in the manufacture of an organic electroluminescent device to form a hole injection layer by spin coating it on an ITO (indium tin oxide) electrode. The PEDOT-PSS material has the following structure:

When a hole injection layer is formed using the composition including PEDOT as a conducting polymer doped with PSS as a polyacid, PSS absorbs moisture well, and thus it is not recommended to incorporate PSS into PEDOT when the removal of moisture is required. Further, PSS can be decomposed by reaction with electrons to release a by-product such as sulfate, which may be diffused to an adjacent organic film, for example, an emissive layer. PEDOT-PSS also contains other impurities of alkaline metals such as Na. This diffusion of the material derived from the hole injection layer to the emissive layer induces exciton quenching resulting in a reduction in the efficiency and lifetime of the organic electroluminescent device. In addition, the diffused by-products may initiate the formation of insoluble layer which was usually observed in polymer light-emitting diodes.
Thus, a demand for a novel composition of a conducting polymer is increasing to obtain satisfactory device efficiency and lifetime in an opto-electronic device such as an organic electroluminescent device.